30 ORIGIN OF PHYSICAL CONCEPTS 



The structural dualism of the human body, its 

 / right and left, its front and back, etc., furnish our 

 activity with a set of constant forms to which its 

 action must conform, and which necessarily also 

 partake of, and help us to conceive of tridimensional 

 form. It is interesting to note that this dualism 

 characterises the organs specially adapted to serve 

 exertional action rather than those which serve 

 our vegetal or nutrient life. 



The way in which our spatial conceptions are ever 

 extended and built up out of the data of action is 

 also well illustrated in the case of the blind, and 

 to this also M. Villey devotes an interesting chapter 

 under the title La conquete des representations 

 spatiales. 



This is effected in their case by the high develop- 

 ment of what we must call active touch. Just as 

 we distinguish between hearing and listening, 

 between seeing and looking, so must we distinguish 

 between touching and palpation. 



Mere passive touch gives a certain amount 

 of information, but comparatively little. It is 

 necessary to explore ; that is what is done in active 

 touch palpation of different degrees. 



The sensitiveness of the skin varies at different 

 places from the tongue downwards. Palpation by 

 the fingers marks a further stage. The blind also, 



